Nodular melanoma? Terrified!!

I have had this little red bump on my back tattoo for about a year... and today I noticed that it turned black and it's starting to hurt! I don't look at my back on a regular basis, so I don't know how long its been that color!

I'm 22 years old and melanoma runs in my family... I am convinced that is what it is, and it looks like nodular melanoma, which is usually fatal. I have an appointment with my derm on Monday, but in the meantime I am absolutely panicking...!!

My mom is saying not to worry because its small... what is the definition of a "regular" sized melanoma? It's smaller than a pencil eraser, but it's a raised bump. I have attached two photos.

I know this is NOT good, and I don't know if I can wait until Monday... is this worth going to the ER for? Or should I wait?

Hi,
I know it is easier for me to say that you should not worry, than it is actually for you to do it. But you have to point to worry, cuz you have done everything right - made an appointment to the doctor! So, worry after Monday.